RE: 0003177: Real numbers with scale factors in digital delays

Hi,

There may be a conflict with SystemVerilog on this point.
In SV, a delay value may be a time literal.
This is the description of time literals:

"5.8 Time literals

Time is written in integer or fixed-point format, followed without a space by a time unit (fs ps ns us ms s).
For example:

2.1ns
40ps

The time literal is interpreted as a realtime value scaled to the current time unit and rounded to the current time precision."

Regards,
Shalom

> -----Original Message-----
> From: owner-verilog-ams@eda.org [mailto:owner-verilog-ams@eda.org] On
> Behalf Of Geoffrey.Coram
> Sent: Friday, August 06, 2010 10:16 PM
> To: verilog-AMS LRM Committee
> Subject: Re: 0003177: Real numbers with scale factors in digital delays
>
> Hi, Ken -
> I had a quick look through the 1364 Verilog LRMs, and I found
> that 1364-1995 (on which V-AMS was originally built) and -2001,
>
> delay_value ::=
> unsigned_number
> | parameter_identifier
> | specparam_identifier
> | mintypmax_expression
>
> whereas in 1364-2005,
>
> delay_value ::=
> unsigned_number
> | real_number
> | identifier
>
> I assume the semantics in 2.3.1 just weren't updated to reflect
> the addition of real_number in the BNF when the new BNF was
> brought over from 1364. I support your proposal.
>
> -Geoffrey
>
>
>
> Ken Kundert wrote:
> > All,
> > I have found an inconsistency in the 2.3.1 version of the LRM. In
> > particular on page 15 is says ...
> >
> > Scale factors are not allowed to be used in defining digital
> delays
> > (e.g., #5u).
> >
> > However, the BNF uses delay_value to represent a digital delay, and
> on
> > page 331 it says that delay_value may be a real number, and on page
> 351
> > a real number is allowed to have a scale factor.
> >
> > This conflict within the LRM should be eliminated. I see no reason
> for
> > this restriction, and in fact one existing commercial implementation
> > allows this, seemingly without difficulty. I believe having arbitrary
> > restrictions like this in the language reduces its usability and in
> this
> > case it reduces it readability. I propose that we delete the
> restriction
> > on page 15.
> >
> > I would like to get this issue put on the agenda for an upcoming
> > meeting. It's ID in Mantis is 0003177.
> >
> > -Ken

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